Fiber-reinforced polymer composites have been used in the construction of load bearing articles, typically in marine, automotive, aerospace and construction industries. These composites typically contain fibrous reinforcement such as glass fibres and carbon fibres, embedded in a cured matrix resin.
Fiber-reinforced polymer composites are traditionally made from prepreg sheets of resin-impregnated fibers, which are laid up, molded and cured. The resin content in the prepregs is high, typically 20%-50% by weight. The prepreg properties and quality are controlled for toughness, strength, flexibility and the like. Prepreg sheets may be cut to smaller sizes for laying up in the construction of a given article.
In recent years, resin infusion technologies have been utilized to manufacture complex-shaped structures which are otherwise difficult to manufacture using conventional prepreg technology. Resin infusion technologies include Resin Transfer Molding (RTM), Liquid Resin Infusion (LRI), Vacuum Assisted Resin Transfer Molding (VARTM), Resin Infusion with Flexible Tooling (RIFT), Vacuum Assisted Resin Infusion (VARI), Resin Film Infusion (RFI), Controlled Atmospheric Pressure Resin Infusion (CAPRI), VAP (Vacuum Assisted Process) and Single Line Injection (SLI). Resin infusion differs from that of conventional prepreg technology in that dry structural reinforcement fibers are arranged in a mold as a preform, then the preform is injected or infused directly in-situ with the resin matrix. After resin infusion, the resin-infused preform is cured to form a hardened composite part. The preform typically consists of a plurality of layers of fibrous materials, such as unidirectional fibers or woven fabrics, which are assembled via a layup process to form a predetermined shape and held in place by stitching, stapling or bonding using binders. Preform fabrication often requires the cutting (or slitting) of dry fabrics or fibres to certain size and/or shape. The limitations of these conventional fibrous products lies in the inability to slit and apply these products via an automated lay down process without deforming and fraying the edges.
Binders have been used in the fabrication of dry preforms for various purposes such as to provide cohesion of the reinforcement fibers, to bind layers of reinforcement fibers, and to provide tack so the fibrous material remains in a stationary position during the layup process. Although there are commercially available binders such as solvent-borne binders and binders in powder form, there are disadvantages associated with each type. As such, there remains a need for a binder composition that can be applied in an environmentally friendly manner, and can improve the handling, slitting and shaping of the fibrous materials that are used for the fabrication of dry preforms.